The present invention relates generally to engine driven welding generators. More specifically, it relates to a method and apparatus for controlling the engine speed of a welding generator.
Engine driven generators are commonly used in welding. These welding generators are used extensively in connection with welding operations performed at remote locations where access to conventional utility power is limited or unavailable. Generators are also used by those who perform welding operations at multiple locations because they allow for portability without the need for access to utility power. In addition to a welding output, an auxiliary output (e.g., 120 or 240 volts 60 Hz ac for example) is also typically provided from the welding generator to run power tools, lights, etc . . . .
Engine driven welding generators include an engine (e.g, gasoline, diesel, propane, etc . . . ) and a generator. The term generator, as used herein, may include one or more generator stages or welding power supply stages. The generator stages are driven by the engine. A single generator stage may supply both the welding output and the auxiliary power. In other welding generators, two generator stages are provided, one supplying the welding power and the other supplying the auxiliary power. Both generator stages are driven by the engine. In yet another configuration, one generator stage provides auxiliary power and power to a welding power supply stage. The welding power supply stage receives the power from the generator stage and converts it into a welding output in a similar manner to the way a conventional welding power supply converts utility power into a welding output.
The engine of an engine driven welding generator is typically configured to operate at two speeds. It should be understood, however, that some engine driven welding generators have engines that operate at more than two speeds such as three or more speeds. The lower of the two speeds is referred to as the idle speed. The higher of the two speeds is referred to as the run speed.
The idle speed is the speed at which the engine normally operates when the welding generator is not supplying rated welding output power or auxiliary power. Although some welding generators are configured to provide output power when idling, these generators also operate at the idle speed when not providing output power. The term output power, as used herein in regards to a welding generator, includes both weld power and auxiliary power.
The actual speed at which an engine idles is typically chosen to be at or near the minimum speed required in order to maintain weld integrity when welding first begins (before the engine has a chance to switch to the run speed). Idle speeds for welding generators typically range between 900-2700 rpms with the vast majority of welding generators idling somewhere between 2200-2600 rpms. 1500 and 1800 rpms are also common idle speeds because 50 Hz and 60 Hz auxiliary output power are easily generated at these speeds using a four pole rotor.
Welding generally is performed with the engine operating at run speed. This is because most generators are configured to provide maximum horsepower at run speed. Auxiliary power is also typically provided with engines operating at run speed. Run speed, therefore, is typically the engine speed that will provide the maximum rated welding output power from the generator as well as auxiliary power at the desired frequency directly from the generator (e.g., 50 Hz or 60 Hz for example).
Engine run speeds typically range between approximately 1800-1900 rpms or 3600-3700 rpms. 3000 rpms is also a common engine speed, for example, because 50 Hz auxiliary output power is easily generated at this speed using a two pole rotor. Likewise, 3600 rpms is a common engine speed for providing 60 Hz auxiliary output power.
Prior art engine driven welding generators are configured to sense either a load current or the output power (either at the weld output or the auxiliary output of the generator). If the sensed load current or output power level exceeds a predetermined threshold, the engine automatically switches from idle speed to run speed to meet the demand for output power. The threshold level is generally set at a level that will reliably indicate whether welding is taking place or whether a device connected to the auxiliary output is demanding power. Once the threshold is exceeded, the engine will remain at run speed until the demand for output power stops (e.g, the load current or output power drop below the threshold.
Many prior art welding generators are configured to maintain the engine speed of the engine at the run speed even after the demand for weld power or auxiliary power ceases to exist (e.g., after the load current or output power drop below the threshold). This is because most welds are not made as one long continuous weld, but rather are made up of numerous short repetitive welds. It is common, therefore, for the user of a welding generator to cease welding for a brief period of time to make adjustments to the weld or the welding equipment (e.g., replace a welding electrode). Likewise, the user of a device connected to the auxiliary output may stop using the device briefly to make adjustments. These activities result in a momentary interruption in the demand for output power from the generator. In each of these cases however, a renewed demand for output power from the generator will typically be made within a short period of time.
To prevent the engine from switching back and forth between run speed and idle speed when a brief interruption in the demand for output power occurs, prior art welding generators provide a time delay before the engine slows to idle speed when the demand for output power terminates or is interrupted. Prior art welding generators use the same time delay regardless of the type of welding being performed and regardless of whether it is weld power or auxiliary power that is being provided.
The use of a single time delay can be problematic, however. This is because different types of welding typically require different types of adjustments, some of which may take longer to perform than others. Stick welding, for example, typically requires more adjustments to be made during the welding operation than does MIG or TIG welding. During stick welding, the operator repeatedly stops the welding process to replace the stick electrode and to chip away the slag material that forms on the weld. Electrode replacement and slag removal is generally not required during MIG or TIG welding.
To balance on the one hand the desire for an adequate time delay for each of the various welding types with on the other hand, the desire to not have the engine operate at run speed unnecessarily, prior art welding generators have incorporated a time delay that is a compromise between what is desirable for stick welding and what is desirable for MIG or TIG welding. As a result, prior art welding generators typically incorporate a single time delay of 12-14 seconds which provides a workable compromise. This means, however, that the time delay provided for the operator to perform the necessary adjustments when performing stick welding is shorter than is generally required and the time delay provided for those performing MIG and TIG welding is longer than is generally required.
It is desirable, therefore to have a welding generator that incorporates different length time delays for different types of welding. Preferably, the welding generator will provide a 10-12 second time delay for MIG and/or TIG welding while a 18-20 second time delay will be provided for stick welding. It is also desirable to have a welding generator that incorporates a variable time delay. Preferably, the operator of the welding generator will be able to set the duration of the time delay to meet his or her needs.
Engines used in welding generators typically require a short period of xe2x80x9cwarm-up timexe2x80x9d after they are first started before they can sustain operation at idle speed. This is especially true in cold weather conditions. To provide for this warm-up period, prior art welding generator engines are configured to operate at run speed after the engine is first started and continue to operate at run speed for a period of time immediately after the engine starts. After this time delay, the engine automatically switches to idle speed.
In prior art welding generators, a single device provides the warm-up period time delay and the time delay that is used when the generator stops providing output power. Thus, prior art welding generators incorporate a 12-14 second warm-up time delay before the engine automatically switches to idle speed after first being started. As it turns out, however, a much shorter period of time is typically required to allow the engine to warm up sufficiently to maintain operation at idle speed. For example, as little as a 3-5 seconds is typically all the time that is needed.
Allowing a cold engine to run for an extra 7-11 seconds is problematic in several regards. First, it results in unnecessary wear and tear on the engine. Second, it wastes fuel. And third, it creates an unnecessarily noisy environment for the operator. In addition to the above problems, there is the general perception of operators of welding generators that running the engine at run speed when no power demands are being made on the generator is bad for the generator.
It is desirable, therefore, to have a welding generator that provides a shorter warm-up period for switching the engine to idle speed immediately after the engine is started. Preferably, the duration of the time delay will be approximately equal to the minimum amount of time required for the engine to warm-up sufficiently to sustain operation at the idle speed. It is also desirable to have a welding generator that incorporates a variable warm-up time delay. Preferably, the operator of the welding generator will be able to set the duration of the time delay to meet his or her needs and the environmental conditions at hand.
Another problem with the warm-up time delay utilized by prior art welding generators is that the warm-up period is triggered (e.g, begins) when the ignition switch on the generator is turned to the run position. However, the engine does not start until the ignition switch is turned to the start or crank position and thus cannot begin warming up when the prior art warm-up period begins to run. It is desirable, therefore, to have a warm-up period that begins to run when the engine starts. Preferably, the warm-up period will begin to run when the ignition key is released from the start position with the engine running.
Finally, another problem with prior art welding generators is that they typically do not switch from idle speed to run speed until welding actually begins. This can create problems because the welding process begins when the engine is at idle speed or during the time period when the engine is switching between idle speed and run speed. For example, this can adversely effect the arc starting process as well as the integrity of the weld. It is desirable, therefore, to have a welding generator that can switch to run speed before welding actually begins to allow the engine to be operating at run speed when the demand for welding power is first received. Preferably, the operator will be able to initiate the switch to run power in an efficient and timely manner, such as by activating the trigger of a welding gun or by closing the contacts on a remote control device connected to the welding gun.
According to a first aspect of the invention, a welding apparatus includes an engine, a generator operatively coupled to the engine and an engine speed controller. The generator provides at least one of a welding output or an auxiliary power output. The engine speed controller is configured to control operation of the engine such that the engine operates at a run speed upon starting and then changes speed to an idle speed following a first time delay that is substantially equal to the minimum period of time required for the engine to warm up sufficiently after starting to maintain engine operation at the idle speed.
In one embodiment, the second time delay is different in duration than the first time delay. In other embodiments, one or more of the first and second time delays are variable and their duration can be adjusted by an operator of the welding apparatus.
In another embodiment, the engine operates at the run speed when output power is provided. The engine speed controller provides a second time delay to delay switching of the engine speed to the idle speed when the welding apparatus stops providing output power in this embodiment, thereby permitting continuous operation of the engine at the run speed during brief interruptions in the demand for output power.
According to a second aspect of the invention, a method of operating an engine driven welding generator includes providing a first engine speed control signal to the engine. In response to the first engine speed control signal, the engine is operated at a run speed upon starting and the engine speed is changed to an idle speed after a time delay that is substantially equal to the minimum period of time required for the engine to warm up sufficiently after starting to maintain engine operation at the idle speed.
In one embodiment the method also includes providing a second engine speed control signal to the engine. In response to the second engine speed control signal, the engine operates at the run speed when output power is provided and switching of the engine speed to the idle speed when the welding apparatus stops providing output power is delayed.
According to a third aspect of the invention, a welding apparatus includes an engine, a generator operatively coupled to the engine and an engine speed controller. The engine is capable of operation at a run speed and an idle speed. The generator provides at least one of a welding output or an auxiliary power output. The engine speed controller includes an input for receiving an engine starting signal indicative of the engine starting and provides an engine speed control signal to the engine in response to the engine starting signal.
In one embodiment the engine starting signal is an engine cranking signal provided from an ignition switch. In another embodiment, the engine receives the engine speed control signal and in response operates at the run speed when first started and then automatically changes speed to the idle speed after a time delay. The time delay is substantially equal to the minimum time period required for the engine to warm up sufficiently to maintain engine operation at the idle speed in another embodiment.
In alternative embodiments, the time delay is approximately 3-5 seconds in duration and is a variable time delay that can be adjusted by the operator of the welding apparatus.
According to a fourth aspect of the invention, a method of operating an engine driven welding generator includes providing an engine starting signal indicative of the engine starting and controlling the speed of the engine in response to the engine starting signal. Controlling the speed of the engine includes operating the engine at a run speed when first started and then changing the speed of the engine to an idle speed after a time delay in one embodiment. The time delay is substantially equal to the minimum time period required for the engine to warm up sufficiently to maintain engine operation at the idle speed in another embodiment. The time delay is approximately 3-5 seconds in duration in yet another embodiment.
According to a fifth aspect of the invention, an engine driven welding generator includes an engine. The engine operates at a run speed when first started and then automatically changes speed to an idle speed after a time delay that is substantially equal in length to the minimum period of time required for the engine to warm up sufficiently after starting to maintain engine operation at the idle speed.
According to a sixth aspect of the invention, a welding apparatus includes an engine, a generator operatively coupled to the engine, a first engine speed control circuit and a second engine speed control circuit. The engine is capable of operation at a run speed and an idle speed. The generator provides at least one of a welding output or an auxiliary power output. The first engine speed control circuit provides a first engine speed control signal to the engine such that the engine operates at the run speed when first started and then automatically changes speed to the idle speed after a first time delay. The second engine speed control circuit provides a second engine speed control signal to the engine such that the engine operates at the run speed after the generator stops providing output power and then automatically changes to the idle speed after a second time delay.
The second time delay is different in duration than the first time delay in one embodiment. The first time delay is approximately 3-5 seconds in duration and the second time delay is approximately 10-20 seconds in duration in another embodiment. The first time delay is substantially equal to the minimum time period required for the engine to warm up sufficiently to maintain engine operation at the idle speed and the second time delay is approximately 10-20 seconds in duration in yet another embodiment. In an alternative embodiment, the second time delay is a variable time delay the duration of which can be adjusted by the operator of the welding apparatus.
According to a seventh aspect of the invention, a welding apparatus includes an engine, a generator operatively coupled to the engine and an engine speed controller. The generator provides at least one of a welding output or an auxiliary power output. The engine speed controller is configured to control the engine such that the engine operates at a run speed upon starting and then changes speed to an idle speed after a first time delay and further operates at the run speed after the generator stops providing output power and then changes to the idle speed after a second time delay different in duration from the first time delay.
The first time delay is substantially equal to the minimum time period required for the engine to warm up sufficiently to maintain engine operation at the idle speed in one embodiment and is approximately 3-5 seconds in duration in another embodiment. In an alternative embodiment, the second time delay is approximately 10-20 seconds in duration. The first and second time delays are variable and can be adjusted by an operator of the welding apparatus in other embodiments.
According to an eigth aspect of the invention, a method of operating an engine driven welding generator includes starting the engine. The engine is then operated at a run speed. Next, the engine is switched to an idle speed after a first time delay. Output power is then provided by the engine. The engine then operates at the run speed after the welding apparatus stops providing output power. The engine speed is then switched to the idle speed after a second time delay different in duration from the first time delay.
According to a ninth aspect of the invention, a method of operating an engine driven welding generator includes providing a first time delay signal to control engine speed when the engine is first started. In response to the first time delay signal, permitting the engine to warm up sufficiently at run speed before switching the engine speed to an idle speed. Providing a second time delay signal to the engine different in duration from the first time delay signal. In response to the second time delay signal, permitting continuous operation of the engine at run speed during brief interruptions in the demand for output power.
In one embodiment, the first time delay is approximately 3-5 seconds in duration and the second time delay is approximately 10-20 seconds in duration. In another embodiment, the first time delay is substantially equal to the minimum time period required for the engine to warm up sufficiently to maintain engine operation at the idle speed and the second time delay is approximately 10-20 seconds in duration.
According to a tenth aspect of the invention, an engine driven welding generator includes an engine having a first time delay for changing the speed of the engine to an idle speed after the engine is started and a second time delay, different in duration from the first time delay, for switching the engine to the idle speed after the welding generator stops providing output power.
According to an eleventh aspect of the invention, a welding apparatus includes an engine, a generator operatively coupled to the engine and an engine speed controller. The generator provides at least one of a welding output or an auxiliary power output. The engine speed controller provides a first time delay for changing the speed of the engine to an idle speed after the welding apparatus stops providing a first type of welding power and a second time delay, different in duration from the first time delay, for switching the engine to the idle speed after the welding apparatus stops providing a second type of welding power different from the first type of welding power.
The first time delay is approximately 10-12 seconds in duration and the second time delay is approximately 18-20 seconds in duration in one embodiment. The first type of welding power is a selective one of MIG or TIG welding power and the second type of welding power is stick welding power in another embodiment. The first time delay is a variable time delay that can be adjusted by the operator of the welding apparatus in yet another embodiment.
According to a twelfth aspect of the invention, a welding apparatus includes an engine, a generator operatively coupled to the engine, and an engine speed controller. The generator provides at least one of a welding output or an auxiliary power output. The engine speed controller provides a time delay for changing the speed of the engine to an idle speed after the generator stops providing welding output power. The engine speed controller includes an input for receiving a welding type sense signal indicative of the type of welding output power provided. The duration of the time delay is a function of the welding type sense signal.
According to a thirteenth aspect of the invention, an engine driven welding generator includes an engine. The time delay in switching the engine speed of the engine to idle speed after the welding generator stops providing output power is a function of the type of welding output power provided by the welding generator.